Electric connection structure and electric connection  member

ABSTRACT

There is provided an electric connection member having a substrate, an insulating adhesive layer provided on the substrate, and a conductive interconnect, wherein the electric connection member is provided with a recess that opens at a side of the insulating adhesive layer, the conductive interconnect is disposed in the recess, a metal nano-ink is disposed on the conductive interconnect, and all of the metal nano-ink is contained inside the recess.

BACKGROUND OF THE INVENTION

The present invention relates to electric connection members, mountingstructures of electronic component assemblies, and intermediate membersused for producing electric connection members.

Conventionally, anisotropic conductive films have been used inconnection of circuit boards in liquid crystal displays. For such ananisotropic conductive film, the structure is employed in which metalparticles are dispersed in an insulating adhesive sheet at apredetermined concentration. An anisotropic conductive film is disposedbetween two interconnect patterns, for instance, a display circuit boardand a drive circuit, and heated and pressurized via a support substrate,whereby metal particles dispersed in the film come into contact with thetwo interconnect patterns to ensure the conduction.

In the connection between the two interconnect patterns, however, themetal particles and either interconnect pattern are connected on a pointbasis, and accordingly, when the connected interconnect patterns arebent or when the circuit board or the anisotropic conductive film isexpanded and contracted under heating, the metal particles come off fromthe interconnect patterns, which causes the conduction between the twoelectrically-connected interconnects to be unstable. Aside from that,such an anisotropic conductive film uses a thermosetting adhesive.Accordingly, when a connection interconnect is bent, cracks may occur inan adhesive layer, and in addition, since the contact area between eachinterconnect pattern and metal particles is small, upon application ofheat and pressure, cracks may occur in interconnect patterns because ofmetal particles.

Meanwhile, JP 2003-045517 A discloses an electric connection member inwhich a plurality of elongated lead layers are arranged in parallel toeach other and joined and fixed to a joint substrate formed of a thinplate via an adhesive layer, as well as an electrode substrate. Thedisclosure is described below with reference to, among attacheddrawings, FIG. 6 corresponding to FIG. 1 of JP 2003-045517 A. In anelectric connection member 500 in which a plurality of elongated leadlayers 3 are arranged in parallel to each other and joined and fixed toa joint substrate 5 formed of a thin plate via an adhesive layer 4, thelead layers 3 are formed to have a width narrower than that of eachstrip interconnect 61 of the electrode substrate 600 which is acounterpart in bonding with the electric connection member 500 and inwhich a plurality of strip interconnects 61 are arranged on a surface ofa substrate 6 in parallel to each other and are connection counterpartsof the lead layers 3. With this configuration, electric connection canbe ensured without damaging opposing interconnect patterns.

In the electric connection member 500 described in JP 2003-045517 A, thelead layers 3 are formed on the adhesive layer 4 having a uniformthickness, and the adhesive layer 4 is formed by applying a pressuresensitive adhesive or an adhesive onto the joint substrate 5 (FIG. 6B).When this electric connection member 500 is connected to the electrodesubstrate 600 in which the strip interconnects 61 are formed on thesurface of the substrate 6 or to an electronic component (e.g.,semiconductor device) having an electrode, the adhesive layer 4 can bebonded with both lateral edge portions of a surface of each stripinterconnect 61 (FIG. 6B).

In the electric connection member 500 and the electrode substrate 600 ofJP 2003-045517 A, however, the lead layers 3 project from a surface ofthe adhesive layer 4, and the strip interconnects 61 also project fromthe surface of the substrate 6, so that the surfaces of the adhesivelayer 4 and the substrate 6 are not tightly adhered and bonded to eachother, resulting in low bonding strength (FIG. 6B).

To cope with it, in the electric connection member 500 and the electrodesubstrate 600, a metal nano-ink (which refers to an ink that containsmetal nanoparticles and can sinter at low temperature) is applied ontothe lead layers 3 and sintered between the lead layers 3 and the stripinterconnects 61 at low temperature, thereby increasing the bondingstrength.

When a metal nano-ink 15 is applied onto surfaces of the lead layers 3projecting from the adhesive layer 4, however, upon pressing theelectric connection member 500 against the electrode substrate 600, themetal nano-ink 15 may flow out between the adhesive layer 4 and thesubstrate 6 (FIG. 5), and adjacent lead layers 3 may be short-circuitedthrough a conductive thin film formed by sintering. In addition, when anencapsulated metal nano-ink described in JP 2014-184381 A is used as themetal nano-ink, the metal nano-ink may be scattered as capsules arebroken, which may lead to a short circuit of adjacent lead layers 3.

SUMMARY OF THE INVENTION

An object of the invention is therefore to provide an electricconnection member that has high bonding strength and is free from therisk of short circuit of adjacent electrodes.

The present inventors have made an intensive study to achieve the objectand as a result found that, using an electric connection member whichcomprises a substrate, an insulating adhesive layer provided on thesubstrate, and a conductive interconnect and which is configured suchthat the electric connection member is provided with a recess that opensat a side of the insulating adhesive layer, the conductive interconnectis disposed in the recess, a metal nano-ink is disposed on theconductive interconnect, and all of the metal nano-ink is containedinside the recess, when the electric connection member is pressedagainst a connection target, a projecting electrode of the connectiontarget is inserted into the recess of the electric connection member ofthe invention, and a low temperature sintering reaction of the metalnano-ink occurs, whereby the electrode of the connection target isconnected to the conductive interconnect and also the surfaces of theconnection target and the insulating adhesive layer are tightly adheredand bonded to each other, thus achieving high bonding strength. Inaddition, since the metal nano-ink is disposed in the recess, even whenthe electric connection member is pressed against the connection target,the metal nano-ink is prevented from flowing out between the insulatingadhesive layer and the connection target, and even when an encapsulatedmetal nano-ink is used as the metal nano-ink, the metal nano-ink isprevented from scattering upon breaking of capsules, thus preventingadjacent electrodes from being short-circuited. The invention has beenthus completed.

Specifically, the present invention provides the following (1) to (10).

(1) An electric connection member comprising a substrate, an insulatingadhesive layer provided on the substrate, and a conductive interconnect,

wherein the electric connection member is provided with a recess thatopens at a side of the insulating adhesive layer,

the conductive interconnect is disposed in the recess,

a metal nano-ink is disposed on the conductive interconnect, and

all of the metal nano-ink is contained inside the recess.

(2) The electric connection member according to (1), wherein the metalnano-ink is an encapsulated metal nano-ink that has a plurality of metalnanoparticles covered by a protective agent in a capsule and that formsa conductive thin film upon breaking of the capsule by means of externalstimulus.(3) The electric connection member according to (2), wherein theconductive thin film is formed by breaking the capsule and performingheat treatment at a temperature of less than 200° C.(4) The electric connection member according to (2) or (3), wherein theprotective agent is an amphiphilic molecule, the plurality of metalnanoparticles are dispersed in a hydrophobic organic solvent, and thecapsule is composed of a hydrophilic compound derivative.(5) The electric connection member according to (4), wherein thehydrophobic organic solvent has an n-octanol/water partition coefficientof not less than 2.(6) The electric connection member according to (4) or (5), wherein thehydrophilic compound derivative has a contact angle of not more than 90°with respect to water.(7) The electric connection member according to any one of (4) to (6),wherein the amphiphilic molecule has a hydrophile-lipophile balancevalue of 0 to 13.(8) The electric connection member according to any one of (1) to (7),wherein the substrate is a flexible substrate.(9) A mounting structure of an electronic component assembly in which anelectronic component having an electrode is mounted on the electricconnection member according to any one of (1) to (8), wherein theconductive interconnect and the electrode are joined to each other bysintering the metal nano-ink in the recess of the insulating adhesivelayer, and a surface of the insulating adhesive layer adheres to asurface of the electronic component.(10) An intermediate member used for producing the electric connectionmember according to any one of (1) to (8), the intermediate membercomprising a substrate, an insulating adhesive layer provided on thesubstrate, and a conductive interconnect,

wherein the intermediate member is provided with a recess that opens ata side of the insulating adhesive layer, and

the conductive interconnect is disposed in the recess.

The present invention can provide an electric connection member that,when connected to a connection target having an electrode, exhibits highbonding strength and is free from the risk of short circuit of adjacentelectrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1F are schematic views showing an electric connection memberand mounting structures of electronic component assemblies according tothe present invention. FIG. 1A is a perspective view of an electricconnection member 100 of the invention, and FIG. 1B is a cross-sectionalview thereof. FIG. 1C is a cross-sectional view of the electricconnection member 100 and an electronic component 200. FIG. 1D is across-sectional view of an electronic component assembly in which theelectric connection member 100 is connected to the electronic component200. FIG. 1E is a cross-sectional view of the electric connection member100 and an electronic component 200 with a plurality of electrodes 214different in thickness. FIG. 1F is a cross-sectional view of anelectronic component assembly in which the electric connection member100 is connected to the electronic component 200 having the electrodes214 different in thickness.

FIGS. 2A-2D are schematic views showing intermediate members used forproducing the electric connection member of the invention. FIG. 2A is aperspective view of an intermediate member 101, and FIG. 2B is across-sectional view thereof. FIGS. 2C and 2D are exemplary views eachshowing the case where recesses 113 penetrate through an insulatingadhesive layer 112.

FIG. 3A is a laser micrograph showing an example of a surface conditionof an electrode 214 of an electronic component 200.

FIGS. 4A-4C are views for illustrating an encapsulated metal nano-inkused in the electric connection member of the invention. FIG. 4A is aschematic view showing the encapsulated metal nano-ink, FIG. 4B is aphotograph showing an exemplary encapsulated metal nano-ink actuallymanufactured, and FIG. 4C is a scanning electron micrograph of an edgeportion of a thin film formed when capsules of an encapsulated metalnano-ink are broken (as observed at an accelerating voltage of 5 kVusing JSM-6301F available from JEOL Ltd.).

FIG. 5 is a view showing an electric connection member and an electrodesubstrate shown in FIG. 1(b) of JP 2003-045517 A in combination with ametal nano-ink.

FIGS. 6A-6B are a view showing the electric connection member and theelectrode substrate shown in FIGS. 1(a) and 1(b) of JP 2003-045517 A.

DETAILED DESCRIPTION OF THE INVENTION

An electric connection member, a mounting structure of an electroniccomponent assembly, and an intermediate member used for producing anelectric connection member according to the invention are described indetail below based on the drawings.

1. Electric Connection Member and Mounting Structure of ElectronicComponent Assembly 1.1) Electric Connection Member

An electric connection member of the invention comprises a substrate, aninsulating adhesive layer provided on the substrate, and a conductiveinterconnect, and is configured such that the electric connection memberis provided with a recess that opens at the insulating adhesive layerside, the conductive interconnect is disposed in the recess, a metalnano-ink is disposed on the conductive interconnect, and all of themetal nano-ink is contained inside the recess.

An example of the electric connection member of the invention isdescribed based on FIGS. 1A and 1B.

FIG. 1A is a perspective view of an electric connection member 100 ofthe invention, and FIG. 1B is a cross-sectional view thereof.

In the electric connection member 100 shown in FIGS. 1A and 1B, aninsulating adhesive layer 112 is provided on a substrate 111.

The electric connection member 100 is provided with recesses 113 thatopen at a surface on the insulating adhesive layer 112 side. Each of therecesses 113 has a bottom 113 a, a lateral wall 113 b and an opening 113c. The recess 113 has a depth less than the thickness of the insulatingadhesive layer 112. More specifically, the bottom 113 a is locatedcloser to the substrate 111 than the plane at the same level as that ofthe surface of the insulating adhesive layer 112 opposite from thesubstrate 111 side is, and closer to the surface of the insulatingadhesive layer 112 opposite from the substrate 111 side than the planeat the same level as that of the interface between the insulatingadhesive layer 112 and the substrate 111 is. The size of the recess 113,i.e., the depth of the recess 113 and the size of the opening 113 c aredetermined such that the recess 113 fits with a corresponding electrode214 of an electronic component 200 which is a connection target. Thedepth of the recess 113 refers to a distance from the plane at the samelevel as that of the surface of the insulating adhesive layer 112opposite from the substrate 111 side to the bottom 113 a in the opening113 c.

Conductive interconnects 114 are disposed in the recesses 113. Morespecifically, the conductive interconnects 114 are disposed on thebottoms 113 a of the recesses 113.

A metal nano-ink 115 (or encapsulated metal nano-ink 115 a) is disposedon the conductive interconnects 114. All of the metal nano-ink 115 iscontained inside the recesses 113. In other words, the surface of alayer formed of the metal nano-ink 115 (or encapsulated metal nano-ink115 a) opposite from the conductive interconnect 114 side is lower thanthe surface of the insulating adhesive layer 112. The total thickness ofthe conductive interconnect 114 and the layer formed of the metalnano-ink 115 (or encapsulated metal nano-ink 115 a) is less than thedepth of the recess 113.

Whether an electric connection member has the foregoing configuration ornot can be determined by observing the shape of the electric connectionmember. In particular, this can be determined by checking as to whethera metal nano-ink or an encapsulated metal nano-ink, or sintered metalparticles are present in a recess on an insulating adhesive layer side.In addition, when this electric connection member is determined to havethe configuration of an intermediate member to be described later as aresult of observation of the shape, the intermediate member can bedetermined to be the one used only for producing the electric connectionmember of the invention or the one which is used for producing theelectric connection member of the invention and is essential inachieving the object by the invention.

The substrate, insulating adhesive layer and conductive interconnect ofthe electric connection member of the invention are described below. Themetal nano-ink will be described later in “5. Metal Nano-Ink.”

1.1.1) Substrate

While the substrate 111 of the electric connection member may be any ofa rigid substrate, a rigid-flexible substrate and a flexible substrate,a flexible substrate is preferred because of its high flexuralendurance.

A material forming the substrate 111 of the electric connection memberis preferably, but not necessarily, a resin material. Examples of such aresin material include polyethylene terephthalate, polyethylene,polypropylene, polycarbonate, polymethyl acrylate, polyfluoroethylene,ABS resin, nylon, acetal resin, vinyl chloride resin, epoxy resin,melamine resin and phenolic resin. A resin material may be suitablyselected in view of various conditions such as flexibility, mechanicalstrength, heat resistance and price.

An organic or inorganic filler or void may be added to a materialforming the substrate 111 of the electric connection member. Althoughnot particularly limited, exemplary organic fillers include acrylic andurethane polymer particles, exemplary inorganic fillers include silica,alumina, zirconia and calcium carbonate particles, exemplary organicvoids include organic microballoons whose outer shells are formed of athermoplastic resin, a phenolic resin or the like, and exemplaryinorganic voids include inorganic microballoons whose outer shells areformed of silica, alumina, zirconia, Shirasu or the like.

The thickness of the substrate 111 of the electric connection member isnot particularly limited, and a thickness of less than 10 μm is notpreferred because the strength of the substrate (film) would beinsufficient, while a thickness of greater than 250 μm is not preferredbecause the substrate (film) would have too high stiffness and when thesubstrate 111 is connected to a member with three-dimensionalirregularities, such stiffness results in lower conformability to theirregularities.

1.1.2) Insulating Adhesive Layer

The insulating adhesive layer 112 of the electric connection member canbe used repeatedly or in permanent connection depending on the type ofan insulating adhesive forming the layer 112.

An insulating adhesive forming the insulating adhesive layer 112 of theelectric connection member may be an adhesive material or apressure-sensitive adhesive material and is not particularly limited.Examples thereof include polyester, polyurethane, acrylic, epoxy,phenol, silicon, polyolefin, polyimide, vinyl and natural polymers. Thepolymers above may be used alone or in combination of two or more.

In order to enhance adhesion and mechanical and thermal properties, thepolymer above may be mixed with, for instance, any of polyester,polyurethane, acrylic, epoxy, phenol, silicon, polyolefin, polyimide andvinyl monomers and oligomers.

The weight-average molecular weight of the polymer above is notparticularly limited, and is preferably not less than 100,000 and morepreferably in a range of 500,000 to 1,000,000 because heat resistanceand cohesion at high temperature can be improved, thereby reducing theoccurrence of peeling and the generation of air bubbles.

The dielectric constant of the insulating adhesive is not particularlylimited. When the conductive interconnect is formed in the recess of theinsulating adhesive layer, upon pressing an electronic component againstthe electric connection member, an electrode of the electronic componentand the conductive interconnect of the electric connection member are tobe covered by the insulating adhesive, and therefore the insulatingadhesive is preferably a material with a low dielectric constant. Forexample, the dielectric constant is not more than 4 and the dissipationfactor is not more than 0.1 at 1 GHz and 25° C. More preferably, thedielectric constant is not more than 3 and the dissipation factor is notmore than 0.01. Even more preferably, the dielectric constant is notmore than 2 and the dissipation factor is not more than 0.001.

The storage modulus of the insulating adhesive is not particularlylimited, and is in a range preferably of 10³ Pa to 10⁶ Pa and morepreferably of 10⁴ Pa to 10⁵ Pa. When the storage modulus is in theabove-defined range, an adhesive can have improved fluidity and hence,the adhesion and the bending behavior are improved, while the stressapplied to a connected portion in expansion and contraction behavior canbe relaxed, so that the adhesive can have improved resistance to bondingbreakage, thus leading to improved adhesion.

The insulating adhesive is preferably a reactive adhesive compositioncontaining a polymerizable compound. Such a composition makes itpossible to connect the electric connection member to a member to bemounted with the optimal adhesion strength.

Examples of such a polymerizable compound include radicallypolymerizable compounds and cationically polymerizable compounds. Apolymerizable compound is not limited as long as it becomes a highmolecular weight compound through polymerization reaction and as aresult improves the adhesion to a material to be mounted, and may be amonomer or an oligomer.

Examples of radically polymerizable compounds include radicallypolymerizable compounds each having a radically polymerizable functionalgroup, such as monofunctional and multifunctional acrylates, maleimide,thiol and vinyl ether.

Examples of cationically polymerizable compounds include cationicallypolymerizable compounds each having a cationically photopolymerizablefunctional group, such as epoxy, oxetane and vinyl ether.

The radically polymerizable compounds and cationically polymerizablecompounds above may be used alone or in combination of two or more.

The polymerizable compound content of an adhesive composition is notparticularly limited, and is in a range preferably of 10 mass % to 80mass % and more preferably of 30 mass % to 60 mass % of the adhesivecomposition. When the polymerizable compound content is in theabove-defined range, the storage modulus after curing is small and theshock resistance is improved, so that the insulating adhesive layer isnot easily broken at low temperature, while a cohesive force aftercuring is sufficiently improved and hence, the adhesion and the heatresistance are improved.

Examples of a polymerization initiator for a polymerizable compoundinclude radical polymerization initiators that are activated by externalenergy such as light or heat to generate radicals, and cationicpolymerization initiators that generate cations. The polymerizationinitiators above may be used alone or in combination of two or more.

The radical polymerization initiator is not particularly limited as longas it enables radical polymerization of a radically polymerizablecompound to proceed with relatively low energy, and examples thereofinclude radical polymerization initiators that generate a startingradical with a single molecule and radical polymerization initiatorsthat generate a radical through reaction between two molecules.

Examples of polymerization initiators that generate a starting radicalwith a single molecule include compounds such as acetophenone,acylphosphine, titanocene, tyrodine and bisimidazole.

Examples of polymerization initiators that generate a radical throughreaction between two molecules include compounds such as benzophenone,amine and thioxanthone.

The cationic polymerization initiator is not particularly limited aslong as it enables a cationically polymerizable compound to bepolymerized with relatively low energy, and examples thereof includeionic acid-generating cationic polymerization initiators and non-ionicacid-generating cationic polymerization initiators.

Examples of ionic acid-generating cationic polymerization initiatorsinclude compounds such as iodonium salt and sulfonium salt.

Examples of non-ionic acid-generating cationic polymerization initiatorsinclude compounds such as sulfonyl diazomethane, oxime sulfonate, imidesulfonate and nitrobenzyl sulfonate.

The amount of added polymerization initiator is not particularly limitedand may be suitably set according to the reactivity of a polymerizablecompound, the amount of molecules, the viscoelasticity desired to beimparted to an adhesive layer, and other factors. More specifically, theamount of added polymerization initiator is set to be in a rangepreferably of 0.001 to 10 mass % and more preferably of 0.1 to 5 mass %with respect to the total weight of polymerization compound(s). When theamount of polymerization initiator is in the above-defined range, thereactivity of the adhesive composition is sufficiently low, so thatcuring by external energy such as light or heat proceeds at moderatespeed and the operation is not hampered, while problems should not occursuch as insufficient curing and decreased curing rate.

In addition, particles made of an inorganic oxide, a resin or the likemay be dispersed in the adhesive composition in order to improve, forinstance, thermal and mechanical properties. The particles made of aninorganic oxide is not particularly limited, and examples thereofinclude particles made of metal oxides such as silica and alumina.Examples of particles made of a resin include particles made ofsynthetic resins such as acrylic resin, styrene resin, fluororesin andsilicone.

The method of providing the insulating adhesive layer on the substrateis not particularly limited, and exemplary methods include variousmethods using coating devices such as a comma coater, various printingmethods such as gravure printing, and methods using a dispenser or aspray.

1.1.3) Conductive Interconnect

Examples of a conductive material that may be used to form theconductive interconnects 114 include metal materials such as copper,silver, gold, platinum, carbon, nickel, palladium, rhodium, rutheniumand indium. The metals above may be used alone or in combination of twoor more. Conductive particles may be plated and be in a spherical, chainor flake-like shape. Use may be made of a conductive interconnect formedby printing a substance in which the conductive material above isdispersed in a binder resin such as urethane resin by a certain printingprocess, followed by baking.

A conductive interconnect formed by using a metal nano-ink to bedescribed in “5. Metal Nano-Ink” below is also preferable.

The width and thickness of the conductive interconnect 114 are notparticularly limited as long as the conductive interconnect 114 can bedisposed in the recess 113. More specifically, the conductiveinterconnect 114 is not greater in width than the recess 113. The widthof the conductive interconnect 114 is preferably not less than 1 μmbecause the manufacture thereof can be easier, and more preferably notless than 5 μm and even more preferably not less than 10 μm in order toreduce the amount of flowing current per unit volume. The thickness ofthe conductive interconnect 114 is less than the depth of the recess113.

Exemplary methods of providing the conductive interconnect 114 in therecess 113 of the electric connection member 100 include various methodsusing coating devices such as a comma coater, various printing methodssuch as gravure printing, and methods using a dispenser or a spray.

1.2) Mounting Structure of Electronic Component Assembly

The mounting structure of an electronic component assembly according tothe invention is a mounting structure of an electronic componentassembly in which an electronic component having an electrode is mountedon the electric connection member of the invention and is configuredsuch that the conductive interconnect and the electrode are joined toeach other by sintering a metal nano-ink in the recess of the insulatingadhesive layer, and a surface of the insulating adhesive layer adheresto a surface of the electronic component.

One example of the mounting structure of an electronic componentassembly according to the invention is described below based on FIGS. 1Cto 1F.

FIG. 1C is a cross-sectional view of the electric connection member 100and an electronic component 200. FIG. 1D is a cross-sectional view of anelectronic component assembly in which the electric connection member100 is connected to the electronic component 200. FIG. 1E is across-sectional view of the electric connection member 100 and anelectronic component 200 with a plurality of electrodes 214 different inthickness. FIG. 1F is a cross-sectional view of an electronic componentassembly in which the electric connection member 100 is connected to theelectronic component 200 having the electrodes 214 different inthickness.

The mounting structure of an electronic component assembly in which anelectronic component having an electrode is mounted on the electricconnection member of the invention is described.

The electric connection member 100 is as described in “1.1) ElectricConnection Member.”

In an electronic component 200, electrodes 214 are disposed on asubstrate 211. Each of the electrodes 214 of the electronic component200 is less in width than the recess 113 of the electric connectionmember 100 so that the electrode 214 can fit in the corresponding recess113. A distance d1 from the plane at the same level as that of thesurface of the insulating adhesive layer 112 opposite from the substrate111 side to the upper surface of the conductive interconnect 114 in theopening 113 c of the recess 113 of the electric connection member 100 isset to be less than the thickness d2 of the electrode 214 of theelectronic component 200.

When the electric connection member 100 is connected to the electroniccomponent 200, as shown in FIG. 1C, the electrodes 214 of the electroniccomponent 200 are fitted into the corresponding recesses 113, and theelectrodes 214 of the electronic component 200 are pressed against theconductive interconnects 114. Thus, the electric connection member 100and the electronic component 200 are connected to each other as shown inFIG. 1D. At this time, as shown in FIG. 1D, the insulating adhesivelayer 112 adheres to the substrate 211, thereby establishing mechanicalbonding.

When pressed, the insulating adhesive layer 112 of the electricconnection member 100 elastically deforms and adheres to the substrate211 of the electronic component 200, and in addition, an elasticrestoring force acts on the substrate 111 of the electric connectionmember 100 as a load exerted in a direction in which the substrate 211of the electronic component 200 is pressed, thus establishing stableelectrical connection between the electric connection member 100 and theelectronic component 200. This electric connection member 100 isconfigured to have a mechanical connecting and fixing structure using aninsulating adhesive layer, and accordingly, can be fixed in a thin shapewith a simple structure and without the need for a dedicated fixing jig.

When a surface of the electrode 214 has the arithmetic mean roughness(Ra), even when the electrode 214 is apparently in surface contact withthe conductive interconnect 114, the contact is actually made up ofpoint contacts, and there are many portions making no contact, that is,many micro gaps. Such micro gaps are filled with the metal nano-ink 115or a metal nano-ink discharged by breaking capsules of the encapsulatedmetal nano-ink 115 a, which is subsequently sintered to form aconductive thin film 116, whereby good electrical connection between theelectrodes 214 and the conductive interconnects 114 can be ensured. Alaser micrograph is shown in FIG. 3 as an example of an electricalconnection surface condition of the electrode 214 of the electroniccomponent 200.

Even when the plurality of electrodes 214 of the electronic component200 are different in thickness as shown in FIGS. 1E and 1F, gaps betweenthe electrodes 214 and the conductive interconnects 114 are filled withthe metal nano-ink 115 (or encapsulated metal nano-ink 115 a) disposedon the conductive interconnects 114, which is sintered to form theconductive thin films 116, whereby good electrical connection betweenthe electrodes 214 and the conductive interconnects 114 can be ensured.

Whether a mounting structure of an electronic component assembly has theforegoing configuration or not can be determined by detaching anelectronic component and observing the component in destructiveinspection. In particular, it is preferable to confirm a sign of theconnection between a conductive interconnect and an electrode viasintered metal particles in a recess located on an insulating adhesivelayer side.

1.2.1) Electronic Component

The electronic component 200 includes the substrate 211 and theelectrodes 214 disposed thereon.

1.2.1.1) Substrate

For the substrate 211 of the electronic component 200, any substrate maybe used without limitation as long as it is for use in surface mountingtype electronic devices. For instance, a substrate of the same type asthe substrate 111 of the electric connection member 100 as above may beused.

1.2.1.2) Electrode

For the electrode 214 of the electronic component 200, any electrode maybe used without limitation as long as it is for use in surface mountingtype electronic devices. For instance, an electrode of the same type asthe conductive interconnect 114 of the electric connection member 100 asabove may be used.

The type of the electronic component 200 is not particularly limited,and examples thereof include a large scale integration (LSI), anintegrated circuit (IC), a liquid crystal display, a transistor, adiode, a light emitting diode (LED), a transistor and a capacitor.

The electronic component 200 is preferably a surface mounting typeelectronic component.

2. Intermediate Member Used for Producing Electric Connection Member

An intermediate member used for producing the electric connection memberof the invention (also simply referred to as “intermediate member of theinvention” or “intermediate member”) comprises a substrate, aninsulating adhesive layer provided on the substrate, and a conductiveinterconnect, and is configured such that the intermediate member isprovided with a recess that opens at the insulating adhesive layer side,and the conductive interconnect is disposed in the recess.

An example of the intermediate member of the invention is describedbelow based on FIGS. 2A to 2D.

FIG. 2A is a perspective view of an intermediate member 101 of theinvention, and FIG. 2B is a cross-sectional view thereof.

In the intermediate member 101 shown in FIGS. 2A and 2B, an insulatingadhesive layer 112 is provided on a substrate 111.

The intermediate member 101 is provided with recesses 113 that open at asurface on the insulating adhesive layer 112 side. Each of the recesses113 has a bottom 113 a, a lateral wall 113 b and an opening 113 c. Therecess 113 has a depth less than the thickness of the insulatingadhesive layer 112. More specifically, the bottom 113 a is locatedcloser to the substrate 111 than the plane at the same level as that ofthe surface of the insulating adhesive layer 112 opposite from thesubstrate 111 side is, and closer to the surface of the insulatingadhesive layer 112 opposite from the substrate 111 side than the planeat the same level as that of the interface between the insulatingadhesive layer 112 and the substrate 111 is. The size of the recess 113,i.e., the depth of the recess 113 and the size of the opening 113 c aredetermined such that the recess 113 fits with a corresponding electrode214 of an electronic component 200 which is a connection target of theelectric connection member 100 produced using the intermediate member101. The depth of the recess 113 is a distance from the plane at thesame level as that of the surface of the insulating adhesive layer 112opposite from the substrate 111 side to the bottom 113 a in the opening113 c.

Conductive interconnects 114 are disposed in the recesses 113. Morespecifically, the conductive interconnects 114 are disposed on thebottoms 113 a of the recesses 113.

The thickness of the conductive interconnect 114 is less than the depthof the recess 113.

While the recess 113 has a depth less than the thickness of theinsulating adhesive layer 112 in an example shown in FIGS. 2A and 2B, inthe intermediate member 101 of the invention, the depth of the recess113 may be greater than the thickness of the insulating adhesive layer112 as long as the recess 113 does not penetrate through the substrate111.

FIG. 2C shows an example of the case where bottoms 113 a of recesses 113are located at the same level as that of the interface between theinsulating adhesive layer 112 and the substrate 111, in other words, thesurface of the substrate 111 on the insulating adhesive layer 112 sideis exposed at the bottoms 113 a.

FIG. 2D shows an example of the case where bottoms 113 a of recesses 113are located close to the surface of the substrate 111 opposite from theinsulating adhesive layer 112 side beyond the plane at the same level asthat of the interface between the insulating adhesive layer 112 and thesubstrate 111, in other words, the recesses 113 are each formed of thecombination of a hole penetrating through the insulating adhesive layer112 and a recess that opens at the surface of the substrate 111 on theinsulating adhesive layer 112 side and is integral with the hole.

Whether an intermediate member has the foregoing configuration or notcan be determined by observing the shape of the intermediate member.

The intermediate member of the invention is used for producing theelectric connection member of the invention and alternatively, may beincluded in a set with a metal nano-ink or an encapsulated metalnano-ink, for example. To be more specific, instead of the electricconnection member of the invention, a set of the intermediate member ofthe invention and a metal nano-ink or an encapsulated metal nano-ink maybe for example provided to a consumer so that the consumer can producethe electric connection member of the invention.

3. Electric Connection Member and Intermediate Member

The electric connection member 100 of the invention is obtained bydisposing the metal nano-ink 115 (or encapsulated metal nano-ink 115 a)on the conductive interconnects 114 of the intermediate member 101, andall of the metal nano-ink 115 (or encapsulated metal nano-ink 115 a) iscontained inside the recesses 113.

Since all of the metal nano-ink 115 (or encapsulated metal nano-ink 115a) is contained inside the recesses 113, the surfaces of the layersformed of the metal nano-ink 115 (or encapsulated metal nano-ink 115 a)disposed on the conductive interconnects 114, opposite from theconductive interconnect 114 side are located closer to the substrate 111than the plane at the same level as that of the surface of theinsulating adhesive layer 112 opposite from the substrate 111 side is.

The method of producing the intermediate member 101 is not particularlylimited. For instance, the intermediate member 101 of the invention maybe produced by disposing or overlaying the insulating adhesive layer 112having the recesses 113 onto the substrate 111. Alternatively, forexample, the intermediate member 101 may be produced by first disposingor overlaying the insulating adhesive layer 112 onto the substrate 111to make a laminated or coated body and then forming the recesses 113from the insulating adhesive layer 112 side of the laminated or coatedbody by cutting or another process. Still alternatively, for example,the intermediate member 101 may be produced by disposing or overlayingthe insulating adhesive layer 112 onto raised portions of the substrate111 having irregularities to thereby form the recesses 113 opening inthe insulating adhesive layer 112.

The electric connection member 100 of the invention can be produced bydisposing the metal nano-ink 115 (or encapsulated metal nano-ink 115 a)or forming a layer of the metal nano-ink 115 (or encapsulated metalnano-ink 115 a) on each conductive interconnect 114 of the intermediatemember 101.

Exemplary methods of disposing the metal nano-ink 115 (or encapsulatedmetal nano-ink 115 a) or forming a layer of the metal nano-ink 115 (orencapsulated metal nano-ink 115 a) on each conductive interconnect 114include various methods using coating devices such as a comma coater,various printing methods such as gravure printing, and methods using adispenser or a spray. As a method of forming a non-encapsulated metalnano-ink layer, an inkjet process is also preferably employed.

For the intermediate member 101, instead of the one in which the depthof the recess 113 is less than the thickness of the insulating adhesivelayer 112 as shown in FIGS. 2A and 2B, the intermediate member 101 inwhich the depth of the recess 113 is the same as the thickness of theinsulating adhesive layer 112 as shown in FIG. 2C may be used. In thiscase, the bottom 113 a of the recess 113 of the electric connectionmember 100 of the invention is located at the same level as that of theinterface between the insulating adhesive layer 112 and the substrate111.

For the intermediate member 101, instead of the one in which the depthof the recess 113 is less than the thickness of the insulating adhesivelayer 112 as shown in FIGS. 2A and 2B, the intermediate member 101 inwhich the depth of the recess 113 is greater than the thickness of theinsulating adhesive layer 112 as shown in FIG. 2D may be used. In thiscase, the bottom 113 a of the recess 113 of the electric connectionmember 100 of the invention is located close to the surface of thesubstrate 111 opposite from the insulating adhesive layer 112 sidebeyond the plane at the same level as that of the interface between theinsulating adhesive layer 112 and the substrate 111.

The recesses 113 are provided at two locations in FIGS. 2A to 2D but maybe provided at one or three or more locations as necessary.

With the depth of the recesses 113 being less than the thickness of theinsulating adhesive layer 112 and the encapsulated metal nano-ink 115 abeing used as the metal nano-ink 115, by forming the conductiveinterconnects 114 having higher hardness than that of the insulatingadhesive layer 112 on the bottoms 113 a of the recesses 113, that is,between the insulating adhesive layer 112 and layers formed of theencapsulated metal nano-ink 115 a, when a pressing force is applied tobreak capsules of the encapsulated metal nano-ink 115 a, a less portionof the force is absorbed by the insulating adhesive layer 112, so thatthe capsules can be sufficiently broken. Therefore, it is preferablethat the depth of the recesses 113 be less than the thickness of theinsulating adhesive layer 112.

4. Advantages of Present Invention over Conventional Art

Advantages of the electric connection member of the invention overconventional electric connection members are described.

When the electric connection member of the invention is pressed againsta connection target such as an electronic component, a projectingelectrode of the connection target is inserted into the recess of theelectric connection member on the insulating adhesive layer side, and alow temperature sintering reaction of the metal nano-ink occurs, wherebynot only the electrode of the connection target is connected to theconductive interconnect of the electric connection member but also thesurface of a substrate of the connection target on the electrode sideand the surface of the electric connection member on the insulatingadhesive layer side are tightly adhered and bonded to each other, thusachieving high bonding strength.

In the electric connection member of the invention, since the metalnano-ink (or encapsulated metal nano-ink) is disposed in the recess,even when the electric connection member is pressed against a connectiontarget, the metal nano-ink is prevented from flowing out between theinsulating adhesive layer and the connection target, and in the casewhere the encapsulated metal nano-ink is used, the metal nano-ink isprevented from scattering upon breaking of capsules, thus preventingadjacent electrodes from being short-circuited.

5. Metal Nano-Ink

Examples of the metal nano-ink include a dispersion of coated ultrafinesilver particles described in JP 2010-265543 A, a dispersion of coatedfine copper particles described in JP 2012-72418 A, a dispersion ofcoated fine metal particles described in JP 2012-162767 A, a dispersionof coated fine silver particles described in JP 2014-31542 A, adispersion of coated fine silver particles described in JP 2014-40630 A,and a dispersion of coated ultrafine silver particles described in WO2011/119630; however, the metal nano-ink is not limited thereto andmetal nano-inks described below may be suitably used.

5.1) Ingredients of Metal Nano-Ink

The metal nano-ink is a low temperature sintering ink comprising metalnanoparticles, a protective agent and a solvent, and is configured suchthat the protective agent is desorbed from the metal nanoparticles asthe solvent evaporates in a room temperature environment, therebyproviding a conductive thin film.

5.1.1) Metal Nanoparticle

The type of the metal nanoparticles above is not particularly limited,and examples thereof include nanoparticles of metals such as gold,silver, copper, platinum, palladium, rhodium, ruthenium, iridium andosmium. Those metals may be used alone or in combination of two or more.

Applicable are metal nanoparticles produced by various known methodssuch as laser ablation, chemical reduction, a process involvingsubjecting an organic metal compound to pyrolysis, a process involvingreducing a metal chloride in a gas phase, and a process involvingreducing an oxide in water.

Metal nanoparticles stabilized by the protective agent and dispersed inthe solvent can be obtained through chemical reduction, and thus use ofmetal nanoparticles synthesized by chemical reduction is particularlypreferred.

The average secondary particle size of the metal nanoparticles above isnot particularly limited, and is in a range preferably of 1 to 500 nm,more preferably of 1 to 100 nm, still more preferably of 1 to 50 nm, andeven more preferably of 1 to 30 nm. When the average secondary particlesize is in the above-defined range, the metal nanoparticles can beeasily stabilized by the protective agent in the solvent, and sinteringtemperature can be lowered. The average secondary particle size ismeasured by dynamic light scattering or laser diffraction. The averagesecondary particle size of metal nanoparticles in an encapsulated metalnano-ink may be measured by, for instance, placing the encapsulatedmetal nano-ink in a suitable organic solvent (which may be hexan,octane, acetonitrile or the like and is preferably the same substance asthe solvent of the metal nano-ink in capsules), breaking capsules in theorganic solvent to dilute the metal nano-ink having been encapsulated,separating capsule residue from a diluted solution by filtration or thelike, and subjecting the obtained diluted solution to dynamic lightscattering or laser diffraction.

5.1.2) Protective Agent

The protective agent above is not particularly limited as long as it canensure the dispersibility of the metal nanoparticles in the solvent, andis preferably an amphiphilic molecule (which is a generic term referringto molecules each containing both of “hydrophilic group” having affinityfor water (aqueous phase) and “lipophilic group” (hydrophobic group)having affinity for oil (organic phase) in the molecule). Thehydrophile-lipophile balance (HLB) value of an amphiphilic molecule(which refers to the degree of affinity of the amphiphilic molecule forwater and oil (water-insoluble organic compound)) is preferably 0 to 13,more preferably 0 to 8, still more preferably 0 to 6, and even morepreferably 0 to 3. When the solvent is a hydrophobic organic solvent, asmaller HLB value is preferred. The HLB value is obtained by identifyingthe protective agent and using the Griffin's method.

Applicable examples of methods for identifying the protective agentinclude methods generally used in organic analysis, such as a nuclearmagnetic resonance method, various chromatography analyses, variousspectroscopic analyses and various mass spectrometry methods. Forinstance, the protective agent can be identified by subjecting the metalnano-ink or a diluted solution thereof to gas chromatography-massspectrometry (GC-MS).

The amphiphilic molecule is preferably at least one selected from thegroup consisting of alkylamines, sorbitan fatty acid ester, polyglycerolfatty acid ester, mercaptan, phosphate ester, aliphatic phosphorusoxide, alkyl amine fatty acid salt, polypropylene oxide fatty acidether, thiol and succinic acid derivatives. Of these, alkylamines arepreferred because these lead to excellent low temperature sinteringproperties and excellent dispersibility of nanoparticles in the solvent.Alkylamine for use may be any of long-chain alkylamine, medium-chainalkylamine and short-chain alkylamine. Alkylamines may be used alone orin combination of two or more. Examples of long-chain alkylamines (inwhich an alkyl group contains 15 or more carbon atoms) includeoleylamine (C₁₈H₃₇N); examples of medium-chain alkylamines (in which analkyl group contains 6 to 10 carbon atoms) include octylamine (C₈H₁₉N)and hexylamine (C₆H₁₅N); and examples of short-chain alkylamines (inwhich an alkyl group contains 1 to 5 carbon atoms) include butylamine(C₄H₁₁N).

5.1.3) Solvent

The solvent above is not particularly limited as long as it can stablydisperse the metal nanoparticles covered by the protective agent, and ispreferably a hydrophobic organic solvent. The hydrophobic organicsolvent preferably has an n-octanol/water partition coefficient of notless than 2 (where, when a chemical substance is dissolved in a liquidhaving two layers of an organic solvent (n-octanol) and water, and theliquid is at equilibrium, the ratio between the amounts of the chemicalsubstance dissolved in the respective solutions is called “partitioncoefficient” and represented by a logarithmic value). In thisspecification, the n-octanol/water partition coefficient (Log₁₀P_(OW))is measured according to JIS Z 7260-117:2006 “Partition coefficient(1-octanol/water).”

Examples of the hydrophobic organic solvent include: aromatichydrocarbons such as benzene, o-toluene, m-toluene and p-toluene;aliphatic hydrocarbons such as n-hexane, n-heptane and n-octane; andhydrocarbon mixtures such as diethyl ether, ligroin (JIS K 8937:1994),petroleum benzine (JIS K 8534:1996) and petroleum ether (JIS K8593:2007).

5.2) Low Temperature Sintering Metal Nano-Ink

The metal nano-ink is preferably a low temperature sintering metalnano-ink and particularly preferably a room temperature sintering metalnano-ink.

The low temperature sintering metal nano-ink is a metal nano-ink thatcan sinter by heat treatment at a temperature of lower than 200° C.,preferably not higher than 150° C., more preferably not higher than 120°C., still more preferably not higher than 100° C., and even morepreferably not higher than 50° C., to thereby form a metal film on asubstrate. The room temperature sintering metal nano-ink is, among lowtemperature sintering metal nano-inks, a metal nano-ink that can sinterat a particularly low temperature, i.e., that can sinter at roomtemperature (with no heating or no cooling from an external system)without heat treatment, to thereby form a metal film on a substrate.

5.3) Encapsulated Metal Nano-Ink

The metal nano-ink is preferably an encapsulated metal nano-ink.

The encapsulated metal nano-ink is an encapsulated metal nano-ink thathas a plurality of metal nanoparticles covered by a protective agent ina capsule and that is capable of forming a conductive thin film uponbreaking of the capsule by means of external stimulus. The schematicview thereof is shown in FIG. 4A. An example of an encapsulated metalnano-ink actually produced is shown in FIG. 4B.

The details of an encapsulated metal nano-ink are described in JP2014-184381 A.

As shown in FIG. 4A, an encapsulated metal nano-ink 50 is composed of atleast a metal nano-ink 52 and a capsule wall 51.

A metal nano-ink (low temperature sintering metal nano-ink) may beencapsulated by any of known methods such as interface reaction, in situpolymerization, in-liquid curing coating, phase separation and in-liquiddrying, which are used as being suitably adjusted in accordance with thepolarity and other properties of an ink solvent.

5.3.1) Metal Nano-Ink

The metal nano-ink 52 is a low temperature sintering ink comprisingmetal nanoparticles 55, a protective agent 54 and a solvent 53, and isconfigured such that the protective agent is desorbed from the metalnanoparticles as the solvent evaporates in a room temperatureenvironment, thereby providing a conductive thin film.

The details of the metal nano-ink are as described above.

5.3.2) Capsule Wall

The capsule wall 51 is not particularly limited as long as it allows themetal nano-ink 52 as encapsulated to be discharged out of a capsule atdesired timing. A capsule is broken for discharging an encapsulated inkout of the capsule. “Breaking” here is preferably a physical process inwhich, for example, a capsule deforms upon receiving pressure and isbroken accordingly. Alternatively, for instance, a process involvingapplying heat to the extent that a metal nano-ink as encapsulated doesnot alter in properties to thereby dissolve a capsule is preferred.Aside from that, it is also possible to discharge an encapsulated inkout of a capsule by using, in combination, a chemical process involvingchanging the equilibrium state between a capsule wall and theencapsulated ink to thereby break the capsule. For example, when acapsule wall is formed of a polymer having any of spiropyrans,azobenzenes, diarylethenes and stilbenes, which are photochromicmaterials, in its molecular skeleton, molecules are isomerized uponirradiation with light, so that the molecular structure changes, wherebythe volume and the electronic structure of the capsule wall change,which allows the degree of interaction between the capsule wall and anencapsulated ink and the mechanical strength of the capsule wall tochange. Aside from that, the physical property of a capsule wall can becontrolled through change in compatibility of a polymer or change involume of a polymer accompanied with electrostatic repulsion by changingthe pH around a capsule to change the ionized state of amino group,carboxy group and hydroxy group. Besides, an electric field may beapplied to a capsule to induce ion transfer or oxidation reduction,whereby physicochemical properties of a capsule wall become non-uniform,which serves to change the equilibrium state. Such stimulus-responsivematerials as above may directly form a capsule or may be dispersed in acapsule as an additive.

5.3.2.1) Hydrophilic Compound Derivative

The capsule wall 51 is preferably composed of a hydrophilic compoundderivative. This is because, when the encapsulated metal nano-inkassumes the form of a dispersion to be described later, the dispersioncan be an aqueous dispersion, leading to good handleability.

The hydrophilic compound derivative preferably has a contact angle ofnot more than 90° with respect to water. When the contact angle is notmore than 90° with respect to water, the hydrophilicity is sufficient.In this specification, the contact angle with respect to water ismeasured according to JIS R 3257:1999 “Testing method of wettability ofglass substrate.”

Examples of the hydrophilic compound derivative include a gel ofalginate obtained by crosslinking water-soluble alginate by the aid ofpolyvalent metal ions (e.g., Ca²⁺, Fe²⁺, Fe³⁺ and Al³⁺), apolyacrylamide gel obtained by crosslinking acrylamide, an agarose gelobtained by dissolving and then cooling agarose, a poly(meth)acrylicacid obtained by polymerizing a (meth)acrylic acid, a mixture ofacrylate and a UV-reactive polymerization initiator (which mixture isirradiated with UV in encapsulation), a photoresponsive polymer in whicha polymer skeleton is modified with any of spiropyrans, azobenzenes,diarylethenes and stilbenes, a pH-responsive polymer having many aminogroups, carboxy groups or hydroxy groups such as polyvinylpyrrolidineand polyethyleneimine, and an electric field-responsive polymer like agel which is formed of an ionic liquid layer and a fluororesin layer andin which ions easily move upon application of voltage. These may be usedalone or in combination of two or more.

5.3.3) Solvent

The encapsulated metal nano-ink may be dispersed in a dispersion mediumto form an encapsulated metal nano-ink dispersion. Owing to such adispersion form, the encapsulated metal nano-ink can have furtherenhanced storage stability.

The dispersion medium above is not particularly limited, and ispreferably water or a hydrophilic solvent in view of dispersionstability when a capsule is formed of a hydrophilic compound derivative.

Examples of the hydrophilic solvent above include water-solublealcohols, ethers derived from water-soluble alcohols and esters derivedfrom water-soluble alcohols.

The water-soluble alcohols above are preferably aliphatic alcoholshaving 1 to 3 hydroxy groups in the molecule, and specific examplesthereof include methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol,1-hexanol, cyclohexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol,glycidol, methylcyclohexanol, 2-methyl-1-butanol, 3-methyl-2-butanol,4-methyl-2-pentanol, isopropyl alcohol, 2-ethylbutanol, 2-ethylhexanol,2-octanol, terpineol, dihydroterpineol, 2-methoxyethanol,2-ethoxyethanol, 2-n-butoxyethanol, carbitol, ethyl carbitol, n-butylcarbitol, diacetone alcohol, ethylene glycol, diethylene glycol,triethylene glycol, tetraethylene glycol, propylene glycol, trimethyleneglycol, dipropylene glycol, tripropylene glycol, 1,2-butylene glycol,1,3-butylene glycol, 1,4-butylene glycol, pentamethylene glycol,hexylene glycol and glycerol.

Examples of the ethers derived from water-soluble alcohols above includediethyl ether, diisobutyl ether, dibutyl ether, methyl-tert-butyl ether,methylcyclohexyl ether, diethylene glycol dimethyl ether, diethyleneglycol diethyl ether, triethylene glycol dimethyl ether, triethyleneglycol diethyl ether, tetrahydrofuran, tetrahydropyran and 1,4-dioxane.

Examples of the esters derived from water-soluble alcohols above includemethyl formate, ethyl formate, butyl formate, methyl acetate, ethylacetate, butyl acetate, methyl propionate, ethyl propionate, butylpropionate and y-butyrolactone. 5.3.4) Average Particle Size ofEncapsulated Metal Nano-Ink

The average particle size of the encapsulated metal nano-ink 115 a isdescribed below with reference to FIGS. 1C and 1D.

The width of the conductive interconnects 114 of the electric connectionmember 100 is assigned with L1, the height of the conductiveinterconnects 114 with H1, the depth of the recesses 113 of the electricconnection member 100 with H2, the thickness of layers formed of theencapsulated metal nano-ink 115 a (hereinafter called “encapsulatedmetal nano-ink layer”) with H3, the arithmetic mean roughness ofelectric connection surfaces of the electrodes 214 of the electroniccomponent 200 when the surfaces have irregularities with Ra, and theaverage particle size of capsules of the encapsulated metal nano-ink 115a with φ.

When L1 is less than 10 μm, it is difficult to finely manufactureelectrode interconnects, and therefore L1 is preferably in a range from10 μm to 300 μm.

The height difference between the upper surface of each conductiveinterconnect 114 and a surface of the insulating adhesive layer 112,i.e., H2−H1, is preferably not less than H3. With H2−H1 being notgreater than H3, when a mounted component is pressed and capsules arebroken, an encapsulated object is to be scattered, and a partitioningeffect by the recesses 113 of the electric connection member 100 isreduced.

Ra is preferably not more than 0.74×H3. With Ra being more than 0.74×H3,even when a mounted component is pressed and the conductive thin films116 are formed on the conductive interconnects 114, it is stillinsufficient to embed the electric connection surfaces with the heightdifference, resulting in unstable electric characteristics.

Preferably, φ is not less than 1 μm. With φ being less than 1 μm, apressing force is to be dispersed, which may make it difficult tosufficiently break capsules. Preferably, φ is not greater than ½ of L1.With φ being greater than ½ of L1, the number of capsules disposed oneach conductive interconnect 114 is to be one, which makes capsulesdifficult to conform to the irregularities at the electric connectionsurfaces of the electrodes 214. The conformability to the irregularitiesat the electric connection surfaces of the electrodes 214 improves withincreasing number of capsules disposed on each conductive interconnect114, and therefore φ is preferably not greater than ⅓ of L1, morepreferably not greater than ¼ of L1, and still more preferably notgreater than ⅕ of L1. Thus, φ is preferably greater than 1 μm and notgreater than ½ of L1, more preferably greater than 1 μm and not greaterthan ⅓ of L1, still more preferably greater than 1 μm and not greaterthan ¼ of L1, and even more preferably greater than 1 μm and not greaterthan ⅕ of L1.

Example

The characteristic features of the present invention are morespecifically described below by way of examples.

However, the present invention should not be construed as being limitedto the examples.

<Production of Encapsulated Metal Nano-Ink>

A metal nano-ink (hereinafter sometimes called “room temperaturesintering ink”) was prepared by the method described in Example 1 of JP2012-162767 A.

Sodium alginate (1.0 g) was weighed and dissolved in Milli-Q water, andthe whole mixture was diluted to 100 mL, thereby preparing a 1.0% (w/v)aqueous sodium alginate solution.

To a 20% (w/v) aqueous calcium chloride solution, 1.0% (w/v) aqueoussodium alginate solution and a room temperature sintering ink were addeddropwise from separate injector-type devices. By placing tip portions ofthe two injector-type devices close to each other and adjusting thedropping rates of the two solutions, the room temperature sintering inkenclosed by the aqueous sodium alginate solution was added dropwise tothe aqueous calcium chloride solution, and the aqueous sodium alginatesolution immediately gelated to encapsulate the room temperaturesintering ink (see FIG. 4B).

After 30 minutes, an encapsulated metal nano-ink having the roomtemperature sintering ink encapsulated by capsules formed of calciumalginate was taken out from the aqueous calcium chloride solution anddried by air at room temperature for 24 hours, thereby producing anencapsulated metal nano-ink. The encapsulated metal nano-ink had anaverage particle size of 3 μm.

What is claimed is:
 1. An electric connection member comprising asubstrate, an insulating adhesive layer provided on the substrate, and aconductive interconnect, wherein the electric connection member isprovided with a recess that opens at a side of the insulating adhesivelayer, the conductive interconnect is disposed in the recess, a metalnano-ink is disposed on the conductive interconnect, and all of themetal nano-ink is contained inside the recess.
 2. The electricconnection member according to claim 1, wherein the metal nano-ink is anencapsulated metal nano-ink that has a plurality of metal nanoparticlescovered by a protective agent in a capsule and that forms a conductivethin film upon breaking of the capsule by means of external stimulus. 3.The electric connection member according to claim 2, wherein theconductive thin film is formed by breaking the capsule and performingheat treatment at a temperature of less than 200° C.
 4. The electricconnection member according to claim 2, wherein the protective agent isan amphiphilic molecule, the plurality of metal nanoparticles aredispersed in a hydrophobic organic solvent, and the capsule is composedof a hydrophilic compound derivative.
 5. The electric connection memberaccording to claim 3, wherein the protective agent is an amphiphilicmolecule, the plurality of metal nanoparticles are dispersed in ahydrophobic organic solvent, and the capsule is composed of ahydrophilic compound derivative.
 6. The electric connection memberaccording to claim 4, wherein the hydrophobic organic solvent has ann-octanol/water partition coefficient of not less than
 2. 7. Theelectric connection member according to claim 4, wherein the hydrophiliccompound derivative has a contact angle of not more than 90° withrespect to water.
 8. The electric connection member according to claim4, wherein the amphiphilic molecule has a hydrophile-lipophile balancevalue of 0 to
 13. 9. The electric connection member according to claim1, wherein the substrate is a flexible substrate.
 10. The electricconnection member according to claim 2, wherein the substrate is aflexible substrate.
 11. The electric connection member according toclaim 3, wherein the substrate is a flexible substrate.
 12. The electricconnection member according to claim 4, wherein the substrate is aflexible substrate.
 13. A mounting structure of an electronic componentassembly in which an electronic component having an electrode is mountedon the electric connection member according to claim 1, wherein theconductive interconnect and the electrode are joined to each other bysintering the metal nano-ink in the recess of the insulating adhesivelayer, and a surface of the insulating adhesive layer adheres to asurface of the electronic component.
 14. A mounting structure of anelectronic component assembly in which an electronic component having anelectrode is mounted on the electric connection member according toclaim 2, wherein the conductive interconnect and the electrode arejoined to each other by sintering the metal nano-ink in the recess ofthe insulating adhesive layer, and a surface of the insulating adhesivelayer adheres to a surface of the electronic component.
 15. A mountingstructure of an electronic component assembly in which an electroniccomponent having an electrode is mounted on the electric connectionmember according to claim 3, wherein the conductive interconnect and theelectrode are joined to each other by sintering the metal nano-ink inthe recess of the insulating adhesive layer, and a surface of theinsulating adhesive layer adheres to a surface of the electroniccomponent.
 16. A mounting structure of an electronic component assemblyin which an electronic component having an electrode is mounted on theelectric connection member according to claim 4, wherein the conductiveinterconnect and the electrode are joined to each other by sintering themetal nano-ink in the recess of the insulating adhesive layer, and asurface of the insulating adhesive layer adheres to a surface of theelectronic component.
 17. An intermediate member used for producing theelectric connection member according to claim 1, the intermediate membercomprising a substrate, an insulating adhesive layer provided on thesubstrate, and a conductive interconnect, wherein the intermediatemember is provided with a recess that opens at a side of the insulatingadhesive layer, and the conductive interconnect is disposed in therecess.
 18. An intermediate member used for producing the electricconnection member according to claim 2, the intermediate membercomprising a substrate, an insulating adhesive layer provided on thesubstrate, and a conductive interconnect, wherein the intermediatemember is provided with a recess that opens at a side of the insulatingadhesive layer, and the conductive interconnect is disposed in therecess.
 19. An intermediate member used for producing the electricconnection member according to claim 3, the intermediate membercomprising a substrate, an insulating adhesive layer provided on thesubstrate, and a conductive interconnect, wherein the intermediatemember is provided with a recess that opens at a side of the insulatingadhesive layer, and the conductive interconnect is disposed in therecess.
 20. An intermediate member used for producing the electricconnection member according to claim 4, the intermediate membercomprising a substrate, an insulating adhesive layer provided on thesubstrate, and a conductive interconnect, wherein the intermediatemember is provided with a recess that opens at a side of the insulatingadhesive layer, and the conductive interconnect is disposed in therecess.